Which two periods have the same number of elements

Periods 2 and 3 have the same number of elements.

Explanation:

I think periods  4 and 5 also have the same number of elements.

your answers are a,b,,e and f

i hope this

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

→